The manufacture of manganese dioxide by electrolysis of an aqueous manganese sulfate/sulfuric acid electrolyte solution in an electrolytic cell is well known. In general, such process involves the passage of an electric current between one or more pairs of electrodes (i.e., a cathode and an anode) submersed in the aqueous electrolyte solution to cause dissociation of the manganese sulfate into manganese (Mn.sup.+2) and sulfate ions. The Mn.sup.+2 ions thus formed then undergo anodic oxidation to form a deposit of manganese dioxide on the anode which anode may be a structure of any of the known materials employed for such use such as lead alloys, graphite, titanium, tantalum, zirconium and the like, and from which the manganese dioxide is subsequently stripped and recovered.
Many materials have been suggested and employed for fabricating cathodic structures for use in electrolytic cells for the manufacture of electrolytic manganese dioxide. Included among such suggested and employed materials are, for example, copper, graphite, mild steel, nickel, platinum and the like. Of these materials, copper is the most commonly employed. However, a disadvantage associated with the use of copper as a cathodic material is its ready tendency to undergo corrosion when contacted with aqueous acidic salt solutions or vapors thereof under electrolytic conditions. As a result of this corrosion, contamination of the manganese dioxide end product with copper oxidization products can occur. The presence of such oxidation products in the manganese dioxide in turn leads to a decrease in both the shelf life and discharge capacity of dry cell batteries manufactured from such contaminated manganese dioxide.
In addition to contamination of the manganese dioxide product, corrosion of cathodes fabricated from copper also adversely affects the overall efficiency and economics of electrolytic processes employing such cathodes. For example, corrosion of the copper cathodes leads to the formation of current inhibiting scales thereon giving rise to increased power demands by the electrolytic cell for the production of a given quantity of the desired electrolytic product and a corresponding increase in production costs. The formation of current inhibiting scales on copper cathodes also gives rise to a need for more frequent replacement of such cathodes than is encountered with cathodes fabricated from other materials such as, for example, graphite. Thus, the need for more frequent replacement of copper cathodes further adds to the cost of producing manganese dioxide by electrolytic processes.